Process for the hydrogenation of halogenonitro-aromatic compounds in the presence of an iodide

Abstract

A process for the preparation of amino halogeno aromatic compounds, according to which a halogenonitro-aromatic compound is brought into the presence of a nickel-, cobalt- or iron-based catalyst, preferably nickel-based, and, more preferably, Raney nickel, in the presence of an effective amount of iodide, at a temperature and hydrogen pressure sufficient to form said halogenoamino-aromatic compound.

What is claimed is: 
     
       1. A process for the preparation of a halogenoamino-aromatic compound having at least one halogen selected from the group consisting of fluorine and chlorine bonded to said aromatic ring comprising the step of contacting in the presence or absence of a solvent a halogenonitro-aromatic compound having at least one halogen selected from the group consisting of fluorine and chlorine bonded to said aromatic ring with hydrogen and a catalytic amount of a hydrogenation catalyst consisting essentially of a metal selected from nickel, cobalt, and iron in the presence of an effective amount of iodide, at a temperature and hydrogen pressure sufficient to form said halogenoamino-aromatic compound. 
     
     
       2. A process as claimed in claim 1 wherein the catalyst is nickel. 
     
     
       3. A process as claimed in claim 2 wherein said nickel is Raney nickel. 
     
     
       4. The process as claimed in claim 3, wherein the halogenonitro-aromatic compound corresponds to the formula   (Z).sub.q (Y).sub.p (X).sub.n --Ar--NO.sub.2     wherein   Ar represents a monocyclic, polycyclic or heterocyclic aromatic radical which may or may not be fused and which may be substituted by an alkyl group containing 1 to 4 carbon atoms,   X, Y and Z each independently represents a halogen selected from fluorine, chlorine and bromine, with the proviso that at least one of X, Y and Z is fluorine or chlorine,   n, p and q each independently represents an integer of between 0 and 5, wherein the sum of n+p+q is greater than or equal to 1.   
     
     
       5. The process as claimed in claim 4, wherein Ar represents a monocyclic aromatic radical, and X and Y represent chlorine and/or fluorine and the sum of n+p is greater than or equal to 1 and less than or equal to 3. 
     
     
       6. The process as claimed in claim 1, wherein the iodide is selected from alkali metal iodides and ammonium iodide. 
     
     
       7. The process as claimed in claim 6, wherein the iodide is potassium iodide. 
     
     
       8. The process as claimed in claim 1, wherein the reaction is carried out in the absence of a solvent. 
     
     
       9. The process as claimed in claim 1, wherein said reaction is carried out in the presence of a solvent selected from water, alcohols and aromatic compounds. 
     
     
       10. The process as claimed in claim 9, wherein the solvent is methanol. 
     
     
       11. The process as claimed in claim 1, wherein the amount of hydrogenation catalyst used is from 1 to 150 g per liter of reaction mixture. 
     
     
       12. The process as claimed in claim 11, wherein the amount of hydrogenation catalyst used is from 1 to 5 g per liter of reaction mixture. 
     
     
       13. The process as claimed in claim 1, wherein the molar amount of iodide calculated per liter of reaction mixture is between 10 -3  M and 10 -5  M. 
     
     
       14. The process as claimed in claim 1, wherein the reaction temperature is from 70° C. to 150° C. 
     
     
       15. The process as claimed in claim 14, wherein said reaction temperature is from 70° C. to 100° C. 
     
     
       16. The process as claimed in claim 1, wherein the hydrogen pressure is from 1 to 100 bars. 
     
     
       17. The process as claimed in claim 16, wherein the hydrogen pressure is from 1 to 40 bars. 
     
     
       18. The process as claimed in claim 17, wherein the hydrogen pressure is from 5 to 25 bars.